I think there are two main paths to collaboration. The first is where a well-known and/or wealthy person has an idea for a story but hasn't the time or ability to pull off the writing, so farms it out to someone else, either a ghost writer who does all the work but gets no recognition (as is usual in celebrities' novels) or a fellow writer who gets a smaller by-line under a big-name author like James Patterson and the advantage of a ready-made readership. Either way, the second writer gets paid well for the work. I don't imagine that's a route open to you.
The second way is to find someone with whom you have a connection, whose style might or might not meld with your own but whose strengths and weaknesses complement yours when it comes to writing. I rather imagine that in such cases friendship comes first, and the writing builds upon the personal relationship which is already established.
If you want to have help in writing, and particularly if you want active collaboration, you must never forget to ask yourself the question "What's in it for the other person?" because as sure as eggs is eggs, that's what anyone else reading your post is going to think. It isn't enough that you believe you have a cool idea for a story. The writers here on Chrons have cool stories coming out of our ears and not enough time to write all our own, so although we're always happy to help anyone with ideas and advice, there's not a lot of incentive to spend the hours upon hours of time and energy needed to embark on a full-blown collaboration with someone we don't know.
So my advice is that you try and make a few friends here among the members. Be active and helpful in thread discussions, take part in the Writing Challenges, help critique work in Critiques, put up some of your own work there when you hit 30 posts, and generally get yourself known. You're much more likely to attract offers of help that way.
In any event, good luck with your story.
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